The present invention relates to temperature probes. Typically such probes comprise an elongate tubular sheath which is closed at one end and open at the other. A temperature sensor such as a thermocouple or a resistance element, is provided in the sheath adjacent the closed end and has leads extending the length of the sheath for connecting the sensor to an external circuit. At the open end, the sheath is fastened to a mounting body which is adapted for securing the complete probe in an operational location, e.g. so that the probe can be screwed into a threaded aperture in a wall of an enclosure with the sheath extending into the enclosure. According to normal practice hitherto, the sheath is made of metal and is braised or welded in a bore extending through the mounting body to form a fluid-tight joint between the sheath and the body.